Containers for liquefied gases



Sept' 24, 1933 R. A. REcK ETAL 3,104,984

CONTAINERS FOR LIQUEFIED GASES Filed Feb. l2, 1959 E? mcg@ United StatesPatent O 3,104,984 CNTAINERS FOR LlQUEFEB GASES Richard A. Reck andCharles S. Wiihelmy, Chicago, El., and Jacques Benveniste, Union, NJ.,assigner-s, by rnesne msignments, to Coach International MethaneLimited, a Bahama corporation Filed Feb. 12, 1959, Ser. No. 792,759 4Claims. (Cl. 117-148) The present invention relates to containers forliquefied gases such as liquid nitrogen `or liquid methane and dealsespecially with such containers having special linings which adapt thecontainers for use in connection with liquefied gases. The inventiondeals also with special coating compositions useful in this connection.

Since many of these gases must be stored and transported at lowtemperatures such as m250" C., the conventional gas storage tanks whichare made of steel or other metals are not satisfactory. At these lowtemperatures the metal tanks become brittle and tend to crack, and theexcessive expansion and contraction is also troublesome.

In attempting to solve the problem, containers have been built whichhave an inner lining of laminated balsa wood. The balsa wood is strongenough to provide structural strength and is light in weight, but thereis the disadvantage that the liquids soak into the wood.

Applicants have discovered that satisfactory containers can be providedby using linings such as balsa wood which are coated with specialcompositions. The special compositions utilized in this inventioninvolve certain epoxy resins in combination with certain llers andbonding agents which are catalyzed with a curing agent. Thesecompositions when applied to the balsa wood or other such liningmaterial are converted to a substantially solid coating which is foundto be resistant to the very low temperatures involved and alsosubstantially impermeable to the liquefied gases. Preferably the coatingis utilized in a thickness of about 1A; inch, although other thicknessesmay be employed satisfactorily.

In preparing the coating composition the epoxy resin is combined withcertain fillers and binders. These lillers and binders may be aluminum`oxide (alumina) and asbestos. We have further discovered that thiscoating composition can also be employed as an adhesive in laminatingthe strips of insulating material making up the lining.

It is an object of the present invention to provide a container for thestorage and transportation of low temperature iluids, the containerhav-ing an outer structure which provides strength to the container andan inner insulating liner which is coated to make it resistant to thelow temperatures and also impermeable to the iluids.

It is another object of the present invention to provide a coatingcomposition especially suited for the construction of containers forliquefied gases.

In the accompanying drawings HG. l is a perspective View of oneembodiment of the present invention showing a container having aremovable top section or cover, and

FG. 2 is a cross-sectional view showing the specialcoating compositionused as an adhesive between the laminations of the container hner.

Invthe drawings, the letter A designates generally the bottom part ofthe container and the letter B designates generally the cover or lid forthe container. Section A is provided with a shell `or outer supportingframework 12 made up of upper horizontal members 13 and 14, lowerhorizontal members 15 and 16, and vertical members 17, 18, 19 and 20.The horizontal and vertical supporting members are held together byscrew bolts 21.

Patented Sept. 24, 1963 ICC Disposed within the framework 12, are piecesof insulating material 22 of varying Width but of substantially the samethickness. The pieces of insulating material 22 can be laminatedtogether by means of an adhesive 23, shown in FIG. 2, preferably thecoating composition of the present invention.

The cavity 25, into which the liquid gas is placed, is lined on allsides 26 and the bottom (not shown) with the coating composition of thepresent invention.

The cover B, of the container, is provided with a plug 30 formed fromthe coating composition of the present invention. The dimensions of plug30 are such that it will completely cover the opening to cavity 25 andprevent the escape of the liquid gas stored in the cavity. Cover B isalso provided with parallel grooves 31 and 32. The dimensions of thesegrooves are such that when cover B is placed `on bottom section A of thecontainer so that surfaces 33 and 134 are in contact with each other,upper horizontal supporting members 13 and 14 will 4lill the space leftby grooves 3'1 and 32, respectively.

in constructing the container of the present invention, pieces of balsawood 22 of varying width but of substantially the same thickness wereemployed. These pieces of balsa wood are cut to the desired lengths andlaminated together to form the bottom section A of the container and thecover or lid B. If desired, the pieces 22 may be so arranged thatsucceeding layers `are at right angles to each other for increasedstrength and rigidity. This type of construction is shown in lowersection 24 of the container and also in cover A.

The pieces of insulating material 22, preferably balsa wood, can belaminated together by an adhesive 23 shown in FIG. 2, preferably thespecial coating composition of the present invention. No clamping of thepieces is required, since the application of a small amount of handpressure `such as to reduce the thickness of the adhesive layer 23 toabout l/l inch is su'icient to obtain a strong bond.

Having constructed the bottom section A and cover B from laminatedpieces of insulating material, .the bottom section A is provided with -asuitable framework 12. The purpose of this framework is to provideadditional support and rigidity to the container. Various materials maybe employed in the construction of the framework such as Wood, steel orlike materials. The vertical and horizontal members may be boltedtogether by means of screw bolts 21 or welded together if steel stock isused.

After the construction of sections A and B, the cavity 25, into whichthe liquid gas is placed, is ready to be lined on all sides and bottomwith the special coating composition of the present invention. Thiscoating composition is produced through the combination of an epoxyresin with aluminum oxide, asbestos, and a curing agent capable ofconverting lthe resin, aluminum oxide, and asbestos into a hard,thermoset solid.

ln preparing this special coating composition, 45 to 53 parts of anepoxy resin having a viscosity of from to 195 poises at 25 C., and anepoxide equivalent of from to 205 (grams of resin containing 1gram-equivalent of epoxide) is combined with 7 to 10 pants aluminumoxide, 35 to 45 par-ts of asbestos, and from 3 to 4.5 parts of a curingagent for converting the thermoplastic epoxy resins into a hard,thermoset composition. Two types of materials are generally employed ascuring agents, [these materials are amines and acid anhydrides. Examplesof amines which can be used are diethylenetriamine,triethylenetetramine, and diethylaminopropylamine. Acid anhydrides suchas phthalic anhydride and dodecenylsuccinic anhydride may also beemployed.

Best results are obtained when the fillers, for example, aluminum oxideand asbestos are mixed together being careful that the aluminum oxide iswell dispersed in the asbestos fiber. Then thecatalyst or curing agentis added to the epoxy resin and welldispersed therein. Thereafter thefillers and the Iresin containing the curing Iagent are introduced intoa mixer and thoroughly agitated together. After thorough mixing hastaken place, the composition is ready to be applied to a surface or toan article.

The cavity 25 is lined on all sides. The bottom is also lined (notshown). This composition may be suitably ftroweled or sprayed on theinsulating material to a thickness of about Ms inch. If it is desiredthat the composition be applied by means of a spray, it is preferredthat successive coats -or layers of the composition be applied, allowingtime between applications for the layers to harden.

After the resinous coating composition has been applied, it is necessaryto allow the composition to cure or to harden into a solid coating.Curing will take place at room temperature and up to 260 C. As has beenpreviously pointed out, a whole range .of curing agents can be utilized.Diethylaminopropylamine works very well as a curing agent at atemperature of about 93 C. When using diethylaminopropylamine, as acatalyst, a curing time of about 1 hour at 93 C. has proved to besatisfactory. A curing time of from 24 to 48 hours is necessary when thecomposition is cured at room temperature.

The plug 30 is likewise formed from Ithe coating composition of .thepresent invention. The coating composition may be applied directly tosurface 33 so that the outer dimensions of the plug are such that itwill completely seal fthe opening to cavity 25. It is preferred that thethickness of plug 30 be greater than the lining of cavity 2S to insurethat the plug ts Well down into vthe cavity. A plug thickness of .about1/2 inch has proven to be very satisfactory.

The invention may be further illustrated by the following specicexamples:

EXAMPLE I Aluminum oxide and asbestos tiber were thoroughly mixed,making certain that the aluminum oxide was thoroughly dispersed in theasbestos, and then set aside 'to .await the mixing of the resin andcuring agent.

An epoxy resin (Epon 828, Shell Chemical Corporation) (epichlorohydrin/bisphenol A-type, a glycidyl polyether of dihydric alcohol) having aviscosity of from 135 to 195 poises at 25 C. and an epoxide equivalentof from 185 to 205 was Well dispersed with diethylaminopropylamine.Thereafter the mixture of alumina and asbestos was added slowly to -theresin mixture, taking care to insure thorough mixing in au internal typemixer.

Balsa wood specimens of 1 x 1 x 2 inch dimension were coated on allsides tto a thickness of l/s" and cured one hour at 200 F. The coatedspecimens were then immersed into liquid nitrogen for 24 hours (-325 F.)and inspected for cracks and permeability. Coatings that developedcracks, checks or that proved to be permeable to the liquid gas wererejected. The following compositions (in parts by weight) exhibited nosurface cracks or flaws.

Y 1 Epen 828 (Shell Chemical Corporation).

2 Dlethylaminopropylamine. All figures represent parts by Weight.

EXAMPLE II Inorder to test the suitability of the formulations set forthin Table I as adhesives to be used in laminating aroaese together piecesof insulating material, live samples were prepared of each of the tiveformulations set forth in Table I. Laminates were prepared from pieces lx 1 x 2 inches and squeezed together with a layer of adhesive betweenthem. No clamps were necessary. After curing one hour at 200 F., thelaminated pieces were immersed in liquid nitrogen for 24 hours at 325 F.After the 24 hour period, the samples were removed and examined. Thebond strength was such that delamination would not occur at the woodadhesive interface.

In the same manner, the preparation of one square foot panels, one inchthick, entailed no necessity of clamping the boards together, except forthe application of a small amount of hand pressure such as to reduce thethickness of the adhesive layer to about G inch.

EXAMPLE III Tests were conducted to determine the suitability ofreplacing the alumina and asbestos fillers with other fillers such aswood ilour and finely ground leather. In this test, four parts of theepoxy resin (Epon 828) and one part Wood flour were intimately mixed.Diethylaminopropylamine catalyst was added to the epoxy in the amount of1.25 parts before the addition of the filler.

Small balsa wood specimens (l x 1 x 2 inches) were prepared, coated withthe above composition, cured for one hour at 200 F., and the specimensimmersed in liquid nitrogen for 24 hours. All of the samples wererejected due to excessive expansion of the coating caused by gasformation. No cracks were apparent due to cooling.

The use of finely ground leather as a filler in the above formulationWas investigated. The following formulations Were used:

1 See Table I, footnote (l).

`Sample No. 1 was rejected due to excessive expansion of the coatingprobably caused by gas formation. In order to determine whether a slowercuring cycle would eliminate the gas formation, specimens 2 and 3 wereleft standing at room temperature for 72 hours. The coatings did notharden, whereupon the specimens were cured for one and one-half hours at200 F. in an air circulating oven. The coatings displayed tackiness, butdeveloped no foamy swelling. An additional cure of one hour at 250 F.did not eliminate the tackiness.

Samples 2 and 3 were also subjected to a 250 F./1 hour cure without roomtemperature cure. There was no swelling but the cure was incomplete asevidenced by tackiness and softness at the surface of the coatings.

Sample No. 4 was prepared to determine Whether lthe inclusion of Igepal630, a non-ionic wetting agent, Would facilitate the mixing andapplication of the composition. These conditions were slightly improved.However, no foamy swelling developed.

Sample No. 5 was prepared to determine the eifect of a comparativelylarge amount (11% on the basis of epoxy resin) of catalyst. Applicationof the coating was somewhat easier. In compounding, the epoxy resin andground leather were roller milled andthe catalyst was addedsubsequently. Specimens required a longer curing cycle, 2 hours at 200F. No foamy swelling developed. Two specimens of specimen No. 5 wereimmersed inV liquid nitrogen for 24 hours. They developed cracks and thespecimens were rejected.

The foregoing detailed description has been given for clearness ofunderstanding only and no unnecessary limitations are to be inferredtherefrom.

We claim:

1. The method of producing a lining on the surface of a porous thermalinsulating layer adapted to retain a liquid at low temperature When insurface contact therewith comprising coat-ing the surface with a coatingcomposition formed of 45 to 53 parts by weight of an epoxy resin in theform of a glycidyl polyether of dihydric phenol, and a mixture of 7 to10 parts by Weight of aluminum oxide and 35 to 45 parts by Weight ofasbestos and a curing agent capable of converting the composition to asolid, and curing the coating at a temperature of 20 to 260 C.

2. The method as claimed in claim 1 in Which the porous thermalinsulating layer comprises balsa Wood.

3. The method as claimed in claim 1 in which the 5 curing agent ispresent in an amount within 4the range of 3.0 to 4.5 percent by weight.

4. The method of claim 1, wherein the curing agent is diethyl aminopropylamine.

References Cited in the le of this patent UNITED STATES PATENTS 97,390Goddard Nov. 30, 1869 2,494,920 Warrick Jan. 17, 1950 2,570,958 Lee Oct.9, 1951 2,682,515 Naps June 29, 1954 2,895,936 Archer et al. July 21,1959 2,934,452 Sternberg Apr. 26, 1960 2,943,953 Daniel July 5, 1960FOREIGN PATENTS 516,107 Canada Aug. 30, 1955

1. THE METHOD OF PRODUCING A LINING ON THE SURFACE OF A POROUS THERMALINSULATING LAYER ADAPTED TO RETAIN A LIQUID AT LOW TEMPERATURE WHEN INSURFACE CONTACT THEREWITH COMPRISING COATING THE SURFACE WITH A COOATINGCOMPOSITION FORMED OF 45 TO 53 PARTS BY WEIGHT OF AN EPOXY RESIN IN THEFORM OF A GLYCIDYL POLYETHER OF DIHYDRIC PHENOL, AND A MIXTURE OF 7 TO10 PARTS BY WEIGHT OF ALUMINUM OXIDE AND 35 TO 45 PARTS BY WEIGHT OFASBESTOS AND A CURING AGENT CAPABLE OF CONVERTING THE COMPOSITION TO ASOLID, AND CURING THE COATING AT A TEMPERATURE OF 20* TO 260*C.